http://www.cvedetails.com/product/3264/Mozilla-Firefox.html?...
http://www.cvedetails.com/product/15031/Google-Chrome.html?v...
During 2016, Firefox had 53 code execution CVE reports.
Chrome had 2.
Firefox only has around 8% of the browser marketshare. Chrome sits between 44% and 60% depending on the source. So it's not a case of Firefox being more popular and attracting more people to target it for hacks. It's just worse software.
And then there's just user inconveniences like how Firefox becomes extremely slow if you open multiple heavy tabs. e10s has yet to fix it, currently, if you enable it, it only opens 2 processes, one for the UI, and one for the rendering engine. So the UI itself might not slow to a crawl but all your tabs will still feel slow if you open heavy stuff.
Firefox also has a slower rendering engine. My eyesight isn't great and I browse web pages with zoom active in between 120% and 150% depending on pages. That makes Firefox behave extremely slow on some pages. It's particularly unbearable, on, say, slashdot pages with lots of comments.
For the same reason smooth scrolling is the first thing Firefox users disable in Firefox. Smooth scrolling works fine on Chrome. FF has never managed to implement smooth scrolling in a way that doesn't slow things to a crawl and makes the scrolling look like stuttering or low framerate.
People often rely on Javascript benchmarks to say "Hey firefox is as fast as chrome!!!11!!" but JS is only one part of what makes a browser fast or slow. What about the parts that actually render the page to something your screen can display?
> Firefox 57 should be at least equivalent to Chromium.
Chrome would have had to stop all development years ago for that sentence to be true.